Electret Microphones:The Musician’s Friend

Created by Clarice Stasz for assignment in Music Production taught by Loudon Stearns, Berklee School of Music, www.coursera.org, 2013

Electrets are based on Condenser Microphones, which are known to be

Less sturdy than dynamic mics

Preferred studio mic

Offer larger frequency response for collecting partials than dynamic mics

Require phantom power

Invented 1962

Gerhard Sessler and James West at Bell Labs

Developed to improved telephone communications.

DEFINITION

“An electret microphone is a type of condenser microphone, which eliminates the need for a polarizing power supply by using a permanently charged material.”

http://en.wikipedia.org/wiki/Electret_microphone

Or, A microphone consisting of an electret

transducer in which the foil electretdiaphragm is placed next to a perforated, ridged, metal or metal-coated backplate, and output voltage, taken between diaphragm and backplate, is proportional to the displacement of the diaphragm.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Engineering

Vibrating membrane

Preamp

Itc.nyu.edu

Small size advantage

Openmusiclabs.com

You use them all the time.

Do you make Youtubes?

Electrets are in your laptop and portable phone.

They consist of about 9o% of microphones in use today.

Their quality is surprisingly good for many purposes.

Time for a new recording mic?

Your computer mic is fine for everyday uses, like Skype, taking audio notes.

Music on the same mic may sound tinny because of distortion and limited response. You sound better than what you hear.

Benefits of electret

Very inexpensive, under $1 for lowest quality, hence popular with gearheads

Suits voice recording well

Extremely wide frequency response (from 10Hz to 30kHz ) in best cases.

Sample inexpensive electret

Technically superior

This is according to the technical sound engineer papers . The electret design is supposed to be the most accurate transducer.

Of course, this will be affected by the quality of the production. Nonetheless, theoretically, electrets should be the best.

A look inside one type

Being condensors, they need power so some include an amp.

http://sound.westhost.com/project93.htm

Others include a battery and then connect to the amp.

www.caitches.com

Electrets have a bad reputation with some

Vibrating membrane can wear out in a couple of years

More fragile overall than a dynamic mic

Cheap models mean poor quality

Some users find the bass range unsatisfactory

Disadvantages of lower quality (cheap) models

Output impedance is relatively high

Relatively low sensitivity

Noise is relatively high

Sound level handling ability is low,

typically < 90 dBSPL

Home recording

Today you can find good quality electrets for under $50, with the specs you need in terms of pickup pattern, frequency response, and more. Stereo ominidirectional

with direct plugin to minimize vibration

Performing mics as well.

This looks like a dynamic mic.

It’s an electretspecifically for vocalists to reduce pops, optimize lower frequency response, and minimize distortion. It is also a cardioid design.

One pro’s experience

“The cheap electret mics polarize the diaphragm. This is cheap to make but results in a diaphragm that's quite thick (maybe 20 microns or so).

A back-electret puts that charge on a sheet that's between the backplate and the diaphragm. With this arrangement, you can use a normal diaphragm thickness… so it may be difficult to tell the difference between an electretand an externally polarized condensor mic in performance - that gap is narrowing.”

From “Dale” on Gearslutz.com.

Recommendations

For spoken word or singing with a single instrument, your computer mic could be just fine

For higher quality, and ability to make finer mixes before uploading, explore quality electrets now widely available at moderate prices.

For performing, because electrets are technically the purest transducer, you may want to try one out.

In other words…

Where ten years ago people said the electrets were lousy for serious sound work, this is no longer true.

Major microphone firms make professional level electrets, up into hundreds of dollars.

Given the same price and specs, the back-electret design is your better choice.

Connecting to computer

This is a topic in itself. Try these for help:

http://manual.audacityteam.org/man/Tutorial_-_Connecting_a_Microphone

http://www.ehow.com/how_6362940_connect-electric-condenser-microphone-pc.html

http://support.apple.com/kb/HT2508

Self-evaluation

As a result of this project, I learned:

Three of my music-based mics are electrets: flute, ukulele, and Sony mini-stereo recording.

It is worth using an external electret for my laptop for quality recording.

A lot of sound reference materials require some engineering background to comprehend. I definitely missed some understanding in putting this together.

If I had more time,

I’d have sound samples with various mics to demonstrate differences

I’d use Camtasia to make a video from this PowerPoint with an audio track added

In that last case, I’d reduce all the written slides and have more visuals. For example, I’d open up a mic to show the parts.

If you evaluate this….

Don’t hesitate to note errors,

Or to suggest additions.ukestasz@gmail.com